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Preparation of chloroprene Graft Adhesive-Shanghai Zhen Niu Chemical Co., Ltd.
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Preparation of chloroprene Graft Adhesive
Time:2018-10-31 09:00:02    Page view (708)
1 front words
In recent years, cold adhesive bonding is widely used in the interface and repair of nylon belt, canvas tape and flame retardant belt. PVC full plastic or rubber plastic flame retardant core conveyor belt has been widely used in underground transportation. At present, there is no suitable PVC cold adhesive, and it is seldom repaired by cold bonding method. Polymethyl methacrylate (PMMA) is grafted with chloroprene rubber, and chloroprene grafted adhesive with antioxidant is added. The activation temperature is low, the stickiness retention time is long, and the adaptability is wide. The PMMA side chain of the grafted adhesive is similar to the surface free energy of polyvinyl chloride (PVC), which improves the compatibility of the adhesive with PVC and the bonding strength. The reaction mechanism, preparation process and properties were studied in this paper.
2. Reaction mechanism
The graft copolymerization system of rubber (R) and monomer (M) was carried out according to the free chain reaction. Initiator (B) decomposes to produce active free radicals (I.): B_2I.I. Initiates monomer formation to form monomer free radicals (M.): I. +M M. +IM. Continues to attack other monomers to form monomer growth chain free radicals (P.): M. +M P.I. Attacks rubber to form rubber main chain free radicals (R.): I. +R R. +IP. Transfers to rubber to form (R.): P. +R. R. +P monomer growth to form joints on R. Branch rubber (R-P): M+R. R-PR., P. Self-polymerization or copolymerization to produce chain termination reaction R. +P. R-P_R. +R. R-RP. +P. P-P.
3.
3.1 raw material
Chloroprene Rubber (CR)_A-90 Methyl Methacrylate (MMA) Industrial Solvent Industrial Initiator BPO Chemical Pure Inhibitor HQ Chemical Pure Antioxidant 264 Industrial Viscosifier
3.2 Technology
After plasticizing, chloroprene rubber is dissolved in solvent. After dissolving completely, it is placed in a three-neck bottle with agitator. The temperature is controlled at 85-95 C. A certain amount of initiator BPO is added to continue stirring for 15-20 minutes. The residual BPO is added by dropping MMA and then grafting copolymerization is carried out within 1 h. After 1.5-2 h of reaction, the inhibitor HQ is added to prevent aging. Agent 264, finally add the tackifier, stir evenly discharge.
4. Product performance index
Appearance: Viscosity of brown-yellow translucent viscous liquid: 1000-1500CP solid content: 18%-20% peel strength (PVC-PVC): > 8.0 (kg/2.5cm) storage life: more than half a year
5 results and discussion
The concentration of 5.1 monomer affects the quality of the product.
In the grafting reaction system, the concentration ratio of CR to MMA has a decisive effect on the grafting reaction and the properties of the gel. The experimental results show that the optimum ratio of CR/MMA is 100/60.
5.2. Influence of initiator concentration
The determination of initiator dosage is the main factor to control the polymerization rate. When other conditions are fixed, the polymerization rate is proportional to the square root of initiator concentration. The concentration of initiator increases, the reaction rate increases, and the viscosity of the glue increases. However, when the dosage is higher than 2.4%, the amount of initiator increases, and the molecular weight of polymer decreases, and the viscosity of the system decreases.
5.3 temperature effect
Reaction temperature has a great influence on the grafting reaction. Initiation rate and polymerization rate are very low when reaction temperature is lower than 85 (?) C. When reaction temperature is higher than 95 (?), initiator initiation is too fast, which may lead to explosion polymerization or premature decomposition of initiator and stop polymerization at low conversion stage.
Effect of 5.4 on adhesion of PVC leather material
From the mechanism of grafting reaction, it can be seen that the situation of grafting polymerization is complex. The adhesive force of the glue is not only related to the polymerization rate of the monomer, but also to the grafting efficiency of the monomer. The results showed that the adhesive had better adhesion to PVC leather when the polymerization rate of the adhesive was about 40% and the grafting efficiency was more than 50%.
5.5. Ways to increase graft polymerization rate
Based on the reaction mechanism, CR was first moulded on unequal speed cots before feeding to form a certain number of chain free radicals CR., which is undoubtedly necessary to improve the grafting rate. The optimum feeding time of monomer MMA is about 15-20 minutes after initiator is added, and continuous dropping method is suitable, which can effectively reduce the formation of homopolymer PMMA and improve the grafting rate.
6 knot language
CR - MMA grafted adhesive has the advantages of simple process, strong adhesion and wide applicability, especially solving the problem of PVC bonding. It can be used to repair the protective rubber layer on the belt surface of worn PVC whole core conveyor belt, so that the PVC full plastic or rubber core conveyor belt exposed due to the wear of rubber layer can continue to be used to achieve the purpose of saving money.
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